The RESPIT® approach to allergy immunotherapy developed from the integration of several lines
STANDARDIZED ALLERGEN EXTRACT IMMUNOTHERAPY
Canine atopic dermatitis is a common pruritic skin disease often treated with allergen immunotherapy (AIT). AIT in dogs traditionally begins with attempting to identify clinically relevant environmental allergens. Current allergen testing methodologies and immunotherapy techniques in dogs are not standardized. Immunotherapy with a mixture of allergenic extracts selected based on regional aerobiology rather than intradermal tests or serum IgE assays has been described. The objective of this study was to evaluate the effectiveness of regionally-specific immunotherapy in dogs with atopic dermatitis.
This double-blinded study demonstrated that immunotherapy with a standardized allergen mixture resulted in good to excellent response in 76% of atopic dogs, not significantly different than immunotherapy customized on the basis of intradermal test results.
This case series describes 20 people that were switched from allergen-specific immunotherapy to premixed extracts containing both skin reactive and non-reactive allergens. The authors concluded that allergen-mixture immunotherapy is equally effective and did not find evidence of increased adverse clinical reactions.
Birch and grass pollen sensitive patients were treated with SLIT. Those treated with only birch also improved during the grass pollen season; those treated with only grass also improved during the birch season; those treated with both improved by the greatest degree.
This study concluded that “the choice of IgE assay may have a major influence on the positive/negative results and ensuing treatment recommendations.”
Intradermal tests were performed in duplicate. Three investigators, blinded to the allergen identity, independently scored the reactions. Negative and very strong reactions were found to be consistently graded; mid-range reactions were found to be less reliable than desired of a “gold standard” test.
“It is well established that there is only partial correlation between the serological and intradermal tests; however, the significance of discrepant results is unknown and unstudied.”
“…veterinarians can use either allergen-specific intradermal or IgE serological tests to identify hypersensitivity to common environmental allergens as there is no clear evidence that the response to ASIT is superior using allergens selected by IDT or serology.”
In this article, a leading expert provides guidance on immunotherapy formulation with respect to taking advantage of allergen cross-reactivity.
Variability of allergen-specific immunotherapy formulation
Allergen-specific immunotherapy (ASIT) is often discussed as though it represents a uniform treatment option. In fact, the process of customizing an allergen prescription for a pet is not standardized and there is a great deal of subjectivity involved, even when veterinarians are presented with identical test results.
In an informal survey, 11 veterinary dermatologists were given the same patient history and allergy test results and asked for their immunotherapy recommendations. Among the findings:
• each dermatologist prescribed a unique allergen formulation
• only 2 allergens were prescribed by every participant
• the number of allergens included ranged from 10 to 20
• 28/50 allergens were prescribed by at least one dermatologist
• 16/50 allergens were prescribed by >50% of dermatologists
Oromucosal (SLIT) immunotherapy
During this 6-month trial, skin lesion severity scores, pruritus scores, and methylprednisolone usage all improved. A larger, follow-up study treating multi-sensitive dogs with customized allergen mixtures has now enrolled over two hundred dogs with positive results.
At the University of Florida, Rosanna Marsella, DVM, DACVD has conducted a double-blind, placebo controlled study using customized SLIT allergen mixtures produced by the manufacturer of RESPIT Oromucosal Spray. Of particular note, the study design used atopic dogs with known allergen sensitivity evaluated with an epicutaneous allergen challenge model. The study demonstrated a significant improvement in the treatment group and found the oral spray was safe and well tolerated. Dogs started on a dose of 2 squirts once daily, without an initial up-dosing schedule.
In recent years there has been a shift in human medicine away from administering allergens by subcutaneous immunotherapy (SCIT) in favor of sublingual immunotherapy (SLIT). Many studies have found SLIT to be similarly effective and safer than SCIT.
Blood from five normal greyhound dogs was tested for allergen-specific IgE. Four had highly positive reactions. All received immunotherapy with a standardized mixture of 16 aqueous allergens for 6 months. None of the dogs developed clinical hypersensitivity.
With the high prevalence of clinically irrelevant positive reactions that occur with allergy testing, it should be expected that many of the pets that undergo allergen-specific immunotherapy receive irrelevant allergens, regardless of the selection method.